Directive antenna system



July 15, 1952 w. E. KocK ,2,603,749

DIRECTIVE ANTENNA SYSTEM Filed April 8, 1946 5 Sheets-Sheet 1 I l DEC/EELS l ATTORNEY l DEC/8.51.3

`July l5, 1952 W. E. KOCK DIRECTIVE ANTENNA SYSTEM Filed April' 8, 194e 5 Sheets-Sheet 2 HORIZONTAL VIEW o loz'oaoabs'oe'ow nec/PEE:

-e'o -so -40 -30 -zo -l'o /M/ENTOR W l1E'. KOCK A7' TORNEV July 15, 1952 W E, KOCK 2,603,749

DIRECTIVE ANTENNA SYSTEM Filed Aprii s, 1946 5 shew-sheet s /NVENTOR W E. KOCK A 7' TOR/VE V July l5, 1952 w. E. KocK v 2,603,749

l DIECTIVE ANTENNA SYSTEM Filed April 8, 1946 5 Sheets-Sheet 5 FIG. 2/ rop on sorrou noon /NVENTOQ AT TORMSK Patented July 15, 1,952

UNITED STATES PATENT OFFICE Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application April 8, 1946, Serial No. 660,337

Claims. (Cl. 5250-3353) This invention relates to dielectric transmission systems, to passive radio systems for modifying space waves and to antenna systems comprising lenses.

As disclosed in my copending applications, Serial Nos. 642,722, which issued as Patent No. 2,588,249, March 4, 1952 and 642,723, both filed on January 22, 1946, metallic wave changers, such as polarization shifters, polarization circularizers, prisms and lenses, each comprising a plurality of dielectric channels, may be utilized for modifying or refracting space-propagated microwaves (below one meter) and ultra-short waves (one to ten meters) as, for example, frequency modulated waves. Each channel comprises a pair of parallel spaced walls or plates and the air dielectric therebetween, the plates being of the solid. that is continuous, metal type. In the case of a vertically polarized metallic lens, an aperture or lens diameter, and hence a length or height 4dimension, for one or more of the plates, of several wavelengths is usually employed for the purpose of securing the desired focusing action. Since the length or height of the vertical channel walls is roughly dependent upon the design wavelength, the height of the vertical plates in a microwave lens is relatively small, say, in the order of 1 foot or less to feet, whereas the height or length of the plates in an ultra-short wave lens is exceedingly great, that is, ordinarily 50 to 100 feet.

While the solid plates may be satisfactorily used in the microwave or centimetric lenses, the use of this type of plate in ultra-short or metric lenses is not always feasible, primarily because of difliculties encountered in erecting, supporting and maintaining the exceedingly large plates required. Moreover, the amount of metal used in the large solid plates may be substantial and hence, from an economic standpoint, the use of this type of plate in the ultra-short eld may be objectionable. Accordingly, it is often desirable to avoid the use of solid plates in ultra-short wave lenses and in other types of wave changers. In addition in the microwave field, one or more walls of a type other than solid may be utilized with advantage in certain dielectric guides and dielectric wave changer channels and. in particular, in the dual polarized lattice circular lens described herein.

It is one object of this invention to obtain simple, inexepensive, and easily constructed dielectric guides and channels for use in the microwave and ultra-short wave fields.

It is another object of this invention to modify or refract ultra-short waves in a more simple and economical manner than heretofore achieved.

It is another object of this invention, in a dielectric guide or channel comprising one or more metallic Walls, to utilize a minimum amount of metal.

It is another object of this invention to obtain a metallic lens for refracting waves having different polarizations and the same or different frequencies.\; fWWWWM*Mw-"w""l"M It is another object of this invention to transmit or receive frequency modulated broadcast and telecast Waves in a more satisfactory manner than heretofore achieved.

As used herein the term ellipsoid" is generic to the terms prolate spheroid and oblate spheroid. The terms dielectric guides and dielectric channels have the same denotations as in my copending applications mentioned above.

In accordance with one embodiment of the invention, at least one of the two E-plane conductive side walls of a rectangular dielectric guide, conveying microwaves or ultra-short waves of the TEoi mode, comprises a plurality of linear wires or rods spaced a quarter wavelength or less and positioned parallel to the electric polarization of the conveyed wave. The array or curtain of parallel wires forming the wall constitutes a nonsolid, that is, an apertured or slotted plate, or socalled grid or fence, extending parallel to the direction of propagation. By reason of the spacing between adjacent wires the energy leakage is negligibleor at least relatively small.

In accordance with other embodiments the walls of the various wave changers disclosed in my copending rapplications mentioned above are of the grid type mentioned above. In accordance with other embodiments a lens of the wire or solid type is associated with an ultra-short Wave transmitting antenna having a circular horizontal plane directive pattern, for the purpose of securing a low angle of fire, that is, a narrow vertical plane directive pattern. In another embodiment, an ultra-short wave receiving antenna is equipped with a lens for securing improved reception.

In still another embodiment of the invention a dual polarization cellular lens comprises interlocking horizontal and vertical plates for focusing horizontally polarized and vertically polarized waves. For single frequency or single band operation, the transverse dimensions of the individual cells, each comprising the horizontal plate portions or sections included between a pair of adjacent vertical plates, and the sections of the vertical plates included between the aforesaid horizontal plate sections, are equal, that is, the

cells are each square. For dual band operation the aforesaid transverse dimensions are unequal.

The invention will be more fully understood from the following specication taken in conjunction with the drawing on which like reference characters denote elements of similar function and on which:

Fig. 1 is a perspective view of a rectangular microwave or ultra-short wave dielectric guide constructed in accordance with the invention;

Figs. 2 and 3 are perspective and transverse sectional views, respectively, of a circular guide of the invention;

Fig. 4 is a perspective view of a wave polarizer or circularizer constructed in accordance with the invention;

Fig. -5 is a perspective view of a prism constructed in accordance with the invention;

Fig. 6 is a perspective view of a microwave circular lens comprising wire or grid plates; and

Figs. 7 and 8 are directive patterns for the embodiment of Fig. 6;

Fig. 9 is an end view of a microwave cylindrical lens comprising wire or grid plates and also is a vertical plane center section of the circular lens of Fig. 6 and Figs. 10, 11 and 12 are, respectively, a perspective view, a vertical plane section or trace and a horizontal plane section, of a circular cellular lens comprising -plates of the grid type, and Fig. 13 is a direction pattern for the aforementioned cellular lens Fig. 14 is a perspective view of an ultra-short Wave lens constructed in accordance with the invention;

Figs. 15 and 16 are, respectively, a perspective View and a vertical plane section of a vertically-polarized ultra-short Wave transmitting antenna system comprising a wire lens;

Figs. 17 and 18 are perspective and side views of a horizontally polarized transmitting antenna system comprising a wire lens;

Fig. 19 is a perspective view, Fig. 20 a vertical plane section and Figs. 21 and 22 are horizontal plane sections of an ultra-short wave receiving house lens of the invention, and Fig. 23 is a measured directive pattern of this house lens.

Referring to Fig. 1, reference numeral I denotes an air-lled rectangular dielectric guide connected between a source 2 of radio energy and a load 3. 'I'he guide I comprises top and bottom walls 4 of the solid or continuous metal type, side walls 5 of the grid type and the air dielectric medium bounded by the four walls. Assuming vertically polarized (TEoi) waves are used, the a or H-plane dimension (horizontal) and the b or E-plane dimension (vertical) are, respectively, greater and less than one-half the design wavelengths, as in conventional guides. The flat walls 4 and 5 are parallel to the direction 5 of propagation of the waves conveyed by guide I. The grid walls 5 each comprise a plurality of linear rods or wires 'I positioned parallel to the polarization 8 of the waves and spaced apart a distance s equal to a quarter wavelength or less. In one rectangular guide actually constructed in accordance with Fig. 1 for a design wavelength, A, of 3 centimeters, the rods 1 each have a diameter of about 0.49 inch (0.04m and are spaced 0.3 inch (023A) apart. In Figs. 2 and 3, numeral 9 denotes a circular guide, which may be utilized in place of the rectangular guide I of Fig. 1, and comprises the top and bottom concave solid walls 4 and the concave side grid walls 5. The grid walls comprise curved rods or wires 'I extending parallel, substantially, to the polarization and spaced apart, as in Fig. 1, a quarter wavelength or less.

In operation, the waves supplied by source 2 are conveyed by guide I or 9 to the load 3, in a manner now Well understood in the art. By reason of the critical spacing between the rods 'I the energy leakage through the grid Walls 5 is negligible. Thus, in a test of the rectangular guide described above and having an axial length of 3 inches (2.3).), the loss was only 0.7 decibel.

Referring to Fig. 4, reference numeral I0 denotes a wave changer designed for use in the ultra-short wave field and similar, from an electrical standpoint, to the wave changer illustrated by Fig. 1 of my copending application, Serial No. 642,722, mentioned above. The changer IU comprises a plurality of dielectric channels II, each of which comprises a pair of vertical wire walls or curtains I2 and the air dielectric medium therebetween. The a dimension of each channel is greater than one-half the design wavelength, and the b dimension is several wavelengths. Each wall I2 comprises vertical linear wires I'I attached to a short top horizontal wire I5 and a short bottom horizontal wire I5. The wire curtains or walls I2 are supported and maintained in proper position by two long horizontal wiresI I3 attached to the short top wires I5 and to the two towers I4, and by two long horizontal wires I3 attached to the short bottom wires I5 and to the guy wires I5 and I 6. Each Wall I2 constitutes a rectangular channel plate of the grid type and the linear wires I'I are spaced a distance s less than a quarter wavelength apart. Assuming the operating wavelength is about 3 meters, the wires I7 each have a diameter in the order of a quarter of an inch. As in the dielectric guides of Figs. 1 and 2, the wires I'I are in a plane parallel to the direction 6 of wave propagation. AS explained in my copending application, Serial No. 642,722, the grid plates I2 extend at an angle of 45 degrees to the polarization of the wave incoming to the changer and the phase velocity of the channels is greater than the space phase velocity.

The wave changer I may be of the polarization circularizer type or polarization shifter type. When the changer is used as a circularizer the value of the channel depth dimension d, as measured in wavelengths in the channels, is an odd multiple of a quarter wavelength smaller than the value of d as measured in wavelengths in free space. When used as a shifter, the value of dimension d, as measured in wavelengths in the channels is an odd multiple of a half wavelength smaller than the same depth d as measured in space wavelengths. As also explained in my copending application, Serial No. 642,722, in operation, the circularizer functions to change a xed linear Wave polarization to a circular polarization; and the shifter functions to rotate the wave polarization degrees.

The ultra-short wave prism I8 illustrated by Fig. 5 is similar, from an electrical standpoint, to the prism illustrated by Fig. 6 of my copending application, Serial No. 642,722, and is the same, from a structural standpoint, as the changer of Fig. 4, except that the curtains or walls I 2 are triangular instead of rectangular. Also, the polarization of the waves incoming to the prism is parallel to the walls I2. As explained in the copending application Serial No. 642,722, the phase velocity in the channels II of the prism is greater than the space phase velocity and, in operation, the prism functions to refract or bend the direction of the incoming waves toward the thinner portion of the prism. Thus, on the drawing, the arrows I9 represent the path of the incoming waves, and the arrow 20 extending at an angle to the path |9 represents the direction of the outgoing or emergent waves.

Referring to Fig. 6, numeral 2| denotes a circular plano-concave "fast lens which is similar, in electrical operation, to the circular plano-concave lens disclosed in my copending application Serial No. 642,723. The front face 22 of the lens is flat and the back face 23 is ellipsoidal, as explained in my copending application. The lens 2| comprises a plurality of channels each of which comprises a pair of grid walls or curtains l2, the curtains I2 each comprising a plurality of wires |1 spaced a quarter wavelength or less. The back edge of each curtain is linear and the front edge is curvilinear; and the curtains in each half, left or right, of the lens have different shapes. Thus, the extreme or outer curtains are rectangular whereas, as shown by Fig. 9, the central curtain is deeply concave. The several curtains |2 are supported, and held in position, by the wooden retaining members 24 and, in each curtain, the wire ends forming the concave lens face are preferably, but not necessarily, held in proper position by means of a connecting wire 25. Numeral 26 denotes a pointtype antenna horn positioned on the axis 21 of the lens and, as explained below, at or near the lens focus 28. The horn 26 is connected to a translation device 29 by guides 30 and through a means 3|, well known in the art, for adjusting the position of the horn 26 on the axis 21.

The operation of the antenna system, Fig. 6, is believed to be obvious in View of the disclosure in my application Serial No. 642,723.1 Briefly, in transmission, microwaves or ultrashort waves of, for example, the mean or design wavelength, are supplied by the translation device 29 to guides 30 and horn 26, and a wave having a spherical front is projected toward the lens 2|. The lens 2| converts the spherical front to a plane front and a sharp beam of the point type, as shown by Figs. '1 and 8 discussed below, is established. In reception, the incoming plane front is changed to a spherical front converging on the horn at focus, that is, the incoming rays are focused on the horn. As in the guides of Figs. 1 and 2, the energy loss through the curtain |2 is negligible. The focal length of the lens varies with frequency and accordingly, upon a predetermined change within limits of the operating frequency, the position of horn 26 may be adjusted by means of device 3| to a position such as that denoted by numeral 32 or 33, and so as to coincide with the lens focus. Also, for operation over a band of frequencies, the horn may be positioned so as to secure optimum operation over the band.

Figs. '7 and 8 illustrate, respectively, the measured lil-plane and H-plane directive patterns for a system such as that illustrated by Fig. 6, the patterns being taken at a microwave wavelength of about 3.2 centimeters. In each of these gures numerals 34 and 35 denote the major and minor lobes, respectively, and numeral 36 denotes the half power point of the major lobe. It will be observed that the half power widths of the two major lobes are each about 8.6 degrees so that as stated above the beam is of the point type. The minor lobes 35 in each pattern are more than 20 decibels below the peak of the major lobe and are, therefore, negligible. The measured gain is approximately 24.0 decibels. In practice it has been found that removal of the curved wires 25 does not materially affect the operation of the system. Accordingly. if desired, the Vertical wires |1 may be joined by insulating members, such as ropes or wooden members, whereby a structure requiring only vertical support of the Vertical wires |1 is obtained, and this feature is of particular advantage at the longer ultrashort wavelengths.

Referring to Fig. 9, the plano-concave cylindrical lens 31 has a line focus 38 and comprises a plurality of wire curtains I2 having identical shapes. In operation, as explained in my copending application Serial No. 642,723, the lens functions to focus the rays in one plane only, namely, the plane perpendicular to the focal line 38.

Referring to Figs. 10, 11 and 12, reference numeral 39 denotes a circular lens having a plane front face 22 and an ellipsoidally concave back face 23. The lens comprises a plurality of horizontal curtains 49 and a plurality of vertical curtains 4| interlocking therewith, each curtain comprising a plurality of substantially linear wires 42 spaced approximately a quarter wavelength or less. The intersecting horizontal and vertical curtains form a plurality of rectangular cells 43, the side dimensions ai and a2 of which are each greater than one-half of the mean or design wavelength. For single band operation the side dimensions a1 and a2 are equal, that is, the rectangular cells 43 are square, whereas for dual band operation the dimensions a1 and a2 are unequal, and the rectangular cells are not square. Considered differently, the horizontal curtains form a plurality of focusing channels for horizontally polarized waves and the vertical curtains form a plurality of focusing channels for vertically polarized waves, the phase velocity of each channel and therefore of each cell being greater than the space phase Velocity. Considered from another standpoint, the lens comprises several vertical layers 44 spaced apart horizontally a quarter wavelength or less and each comprising the horizontal and vertical wires 42 which are included in a given vertical plane. In one actually constructed microwave lattice lens. each layer comprises square mesh wire. The several layers are held rigidly together by means of wooden block members 45 and bolts 46.

Reference numerals 41 and 48, Fig. 10, denote a vertical dipole and a horizontal dipole, respectively, and numeral 63 denotes a plane reilector. The dipoles 41 and 48 are positioned at the point focus of the lens 39 and are each connected respectively to a transmitter 5U and a receiver 5| by a line 49.

In operation, Fig. l0, Waves are supplied by transmitter 50 over line 49 to the vertical dipole 41 and a vertically polarized wave having a circular wave front is projected by dipole 41 toward the lens 39. rIhe lens functions to refract the wavelets and to convert the circular wave to a plane wave having a direction of propagation aligned with the lens axis. Since the waves are vertically polarized, the horizontal curtains have substantially no eiect on the waves. In reception, horizontally polarized waves are focused on the horizontal dipole 48; and these waves are not affected by the vertical curtains. The cellular lens therefore constitutes a, dual-polarization focusing refractor for focusing horizontally polarized and vertically polarized waves having equal or unequal mean wavelengths, dependent upon the relation of the dimensions a, and az. The Single curve of Fig. 13 illustrates the measured horizontal and vertical E-plane patterns taken at about 3.2 centimeters, for a square cellular lens constructed in accordance with Fig. 10. As shown in Fig. 13, the half power width 36 of the major lobe 34 is only 8.6 degrees, that is fairly narrow, and the minor lobes 35 are negligible. The measured gain of the lattice lens is about 24.0 decibels. If desired, a, transmitter may be kused in place of the receiver I, or a receiver may be used in place of the transmitter '50, or both of lines 49 may be connected to the same transmitter or to the same receiver. Also, if desired, the dual-polarization single or double band lens of Fig. may comprise plates of the solid type disclosed in my copending application Serial No. 642,723, instead of plates of the grid type.

Fig. 14 illustrates a large ultra-short wave lens 52 which is electrically similar to the microwave lens 2I of Fig. 6. The lens 52 is circularly symmetrical and has a point focus 28. The back face 22 of the lens 52 is at and the front face 23 is ellipsoidally concave that is, prolate spheroidal. More specifically, the lens comprises a plurality of fast dielectric channels II each comprising a pair of wire curtains and each curtain comprising linear wires I1 spaced a quarter wavelength apart or less. The lens is supported by guy wires I3 attached to the towers I4. Since symmetrical curtains may be more satisfactory from a structural or mechanical standpoint, both faces may, if desired, be symmetrical concave, that is, the lens may be of the concavo-concave type disclosed in my application, Serial No. 642,723. In one proposed embodiment designed for 3 meters, the lens 52 is 84 feet square, the curtains I2 being spaced 6.25 feet and the wires I1 in each curtain being spaced 2.5 feet.

The feed or point-type primary antenna for the lens 52 comprises a dipole array 53 positioned at or near the focus 28 and comprising a left sub-array 54 and a right sub-array 55 each comprising eight dipoles 56. The left sub-array 54 is connected throughl a branch line 51 and a switch 58, and the right sub-array is connected through a branch line 59 and a switch 60, to a main line 6I and a translation device 62. Numeral 63 denotes a, plane reflector associated with the array 53.

The operation of the ultra-short wave system of Fig. 14 is substantially the same as that of Fig. 6. In more detail, with both switches 58 and 60 closed, the primary antenna 53, 63 is in effect at the focus and the direction of maximum action is aligned with the lens axis 21. The beam may be shifted or steered to the right or left by opening only one of the switches 58 and 60. Thus, with switch 58 open, only the right sub-array 55, which is displaced from the focus, is energized and the direction of maximum action of the system, including the lens and the primary, is to the left of axis 21; and with switch 60 open, only the left sub-array 54 is energized, and the beam is shifted to the right of the axis 21.

Referring to Figs. 15 and 16, the ultra-shortv wave vertically polarized broadcast antenna system, designed for transmitting frequency-modulated or television modulated waves, comprises a biconical horn antenna 64 of the type disclosed in Patent 2,235,506 to S. A. Schelkunoff, and a lens 65 positioned in the cylindrical mouth apertura' 66 of the biconical horn antenna 64. lThe biconical horn antenna 64 is connected to a transmitter |61 by means of a coaxial line 68 having an inner conductor 69 and an outer conductor 18. The end portion 1I of the inner conductor 69 extends beyond the outer conductor 10 and constitutes a short vertical antenna member positioned in the throat aperture 12 of the biconical horn. Numerals 13 and 14 denote the conical sides of the biconical horn, these sides being attached to the inner and outer line conductors 69, 10, repectively.

The lens 65 has a point focus 28 coincident with a point on the antenna member 1I and an axis 15 aligned with the axis of the horn 64. The

lens comprises a plurality of fast dielectric channels II each comprising a pair of plano-quasielliptical vertical wire curtains I2, which are spaced horizontally a dimension a greater than one-half wavelength apart, and the air dielectric medium therebetween. The curtains I2 are attached to and extend between the conical horn sides 13 and 14 and each comprises a plurality of vertical wires I1 spaced horizontally a quarter wavelength or less. The vertical curtains I2 are disposed radially that is, like the spokes of a wheel, in the horn mouth aperture 66 and hence the width or a dimension of each channel II is slightly tapered. This tapering does not affect the focusing action but, preferably, the elliptical contour of the back edge of each curtain is modified slightly to compensate for this tapered a dimension. The vertical channels have similar depths or thicknesses but, in the case of each channel, the depth is elliptically tapered, substantially, so that focusing action is obtained in all vertical planes containing the primary antenna member 1 I. Considered differently, the vertically polarized lens 65 has a centrally disposed cavity, the outer or front face 22 of the lens being cylindrical and the inside or back face 23 being concave. The inside face or surface 23 corresponds to the surface generated by revolving a section 16 of an elliptical or quasi-elliptical curve about a line 11 passing through the focal point 28 and parallel to both the minor or conjugate axis 18 of the ellipse 19 and the minor axis 80 of the ellipse :BL In short, the lens is cylindrically convex, quasi-ellipsoidally concave; and the inside face is quasi-oblate spheroidal. In all horizontal planes, such as the axial plane 15, the lens cross-section is annular. Each dielectric channel I I of the lens 65 is sectoral since its horizontal cross-section comprises an arc of a circle included between two radii of the circle.

In operation, waves are supplied by transmitter 161 over line 68 to the biconical horn antenna 64, and vertically polarized waves are radiated by the biconical horn antenna system. In the horizontal plane, the directive pattern is circular or nondirectional, that is, omnidirectional, and inthe vertical plane the lens 65 functions to focus the rays so as to produce a sharp low lying beam, as is desired. In other Words, the intensity of the desired ground wave or field is increased and the intensity of the undesired sky wave is decreased, by reason of the focussing action of the lens 65. As in the pyramidal horn and lens combination disclosed in my copending application, Serial No. 642,723, the lens 65 obviates the necessity of using an optimum angle biconical horn in order to secure the desired high gain and vertical plane directivity.

Referring to Figs. 17 and 18 the ultra-short wave horizontally polarized broadcast antenna system comprises a primary antenna 82 of a type well known in the art and a fast metallic lens 83,

` 9 'I'he primary antenna 82 comprises two crossed horizontal dipoles 84 and 85, the dipoles being connected to a transmitter 6l by means of a vertical coaxial line 68. For simplicity, the structure for supporting the vertical line 68 is not illustrated.

The lens 83 comprises a plurality of horizontal annular Wire curtains 86, 8l and 88 supported by the vertical wooden members 24 and each having a circular inner periphery 89 and a circular outer periphery 90. Each pair of horizontal curtains and the included air dielectric constitute a fast dielectric horizontal channel, the vertical spacing between adjacent curtains being greater than a half wavelength. The central curtain B6, the intermediate curtains 8l and the extreme curtains 88 each comprise concentric wires I'I spaced apart a quarter wavelength or less. As shown in Fig. 17, the outer diameters of the several curtains are equal and the inner diameters vary elliptically. The inner diameter of the central curtain is the largest and the equal inner diameters of the top and bottom curtains are the smallest. In other words, the depths of the several horizontal channels diier from each other and, considering the vertical plane, the channel depths are elliptically tapered whereby focusing action is obtained, as in the system of Fig. 15, in all vertical planes containing the primary antenna 82. The horizontally polarized lens 83, Figs. 17 and 18, is similar to the vertically polarized lens, Figs. and 16, in that the lens 83 has a centrally disposed cavity. Also the outer or front face 22 is convex and cylindrical and the back or inside face 23 is concave. The inside surface 23 corresponds, as in the lens 65, to the surface generated by revolving a section 'I6 of an ellipse about a line II passing through the focal point 28 and parallel to both the conjugate axis 'I8 of the ellipse 'I9 and the conjugate axis 80 of the ellipse 8I. In short, the lens 83 is cylindrical convex, quasi-ellipsoidally concave; and the inside face is quasi-oblate spheroidal. In all horizontal planes, such as the axial plane 15, the lens section is annular. Also, each horizontal dielectric channel I l of the lens 83 is annular.

The operation of the system of Figs. 17 and 18 is somewhat similar to that of the system of Fig. 15, the main difference being that the waves emitted by the system of Figs. 17 and 18 are horizontally polarized whereas the waves radiated by the antenna system of Figs. 15 and 16 are vertically polarized. In more detail, in the horizontal plane, the radiation of the primary antenna 82, and of the system 82, 83, is omnidirectional. In the vertical plane, the lens functions to produce a low lying sharp beam, that is, focusing action obtains in the vertical plane but not in the horizontal plane. The band width of the broadcast antenna of Fig. 17 is somewhat broader than that of the conventional turnstile antenna which in order to secure a low lying sharp vertical plane beam, of necessity requires several antenna tiers. Over the band, the mismatch is less in the single tier primary antenna of Fig. 17 than in a multiple tier turnstile antenna. Obviously, other types of primary antennas such as a clover-leaf antenna or a wide band crossed dumbbell antenna may be used in place of the crossed dipoles.

Referring to Figs. 19, 20, 2l and 22, reference numeral 9| denotes a house equipped with a directional ultra-short wave antenna system 92 for receiving horizontally polarized waves having the incoming direction 93. The antenna system 92 comprises a horizontal dipole 94 connected by line 68 to a broadcast receiver 95, a plane reflector 96 adjacent the dipole 94 and a two-channel metallic wire lens 91. The lens 91 comprises three horizontal curtains or grid plates, namely, a bottom curtain 98 installed in the bottom or first floor 99 of the house, a central curtain IIJU in the second or middle floor IUI and a top curtain IU2 in the top floor ID3, each curtain comprising horizontal wires I'I spaced one-quarter or less of the wavelength to be received. The lens is plano-ellipsoidally concave and the dipole 94 is at the lens focus. More particularly, as seen from the dipole, the contour of the concave surface facing the dipole is elliptical in all planes containing the dipole and path or direction 93. Assuming the received wavelength is six meters, the vertical spacing between plates or curtains 99, IUI and |03 is in the order of 9.5 to 14 feet; and this spacing corresponds to the spacing between floors in most buildings.

In operation, the house lens functions to focus the incoming horizontally polarized waves which are propagated along path 93, on the receiving dipole 94, whereby highly directional broadcast reception is secured. Fig. 23 illustrates the measured horizontal E-plane directive pattern for the antenna system 92 and, as shown by this curve of the figure, the major lobe 34 is relatively sharp and the minor lobes 35 are negligible. The measured gain of a system comprising a house lens, dipole and reilector is 7 decibels over the system comprising only a dipole and reflector.

Although the invention has been explained in connection with certain embodiments it should be understood that it is not to be limited to the em- Ibodiments described inasmuch as other apparatus may be successfully employed in practicing the invention.

What is claimed is:

1. An electromagnetic wave lens antenna for focusing an electromagnetic wave having a given propagation direction, and given electric and magnetic pol-arizations, and originating substantially from a predetermined position, comprising a plurality of spaced wire curtains positioned adjacent said predetermined position and parallel to said electric polarization, said curtains having oppositely disposed sets of longitudinal edges comprising the edges of the nearest and furthest wires of each of said curtains from said predetermined position, said sets of longitudinal edges lying in and defining the inner and outer surfaces of said lens antenna, the curvature of one of the two surfaces so defined being greater than the curvature of the other of said surfaces.

2. The lens antenna of claim 1 in which the spacing between adjacent wire curtains is at least one-half wavelength of said wave.

3. The lens antenna of claim 2 in which the said outer surface is substantially plane and the said inner surface is concave.

4. The lens antenna oi claim 2 in which the said outer surface is substantially a right circular cylinder and the said inner surface is an elliptically concave cylinder.

5. The lens antenna of claim 3 and an additional plurality of spaced wire curtains positioned at right angles to said first-mentioned set of wire curtains the nearest and furthest sets of edges of said second plurality of wire curtains lying in and assisting in the definition of said inner and said outer surfaces, respectively, olf said mst-mentioned plurality of wire curtains.

WINSTON E. KOCK.

(References on following page) Name Date Llewellyn Feb. 26, 1946 Katzin Apr. 9, 1946 Feldman Dec. 3, 1946 Hollingsworth Feb. 18, 1947 Hershberger Nov. 11, 1947 Cork Feb. 24, 1948 Korn Feb. 24, 1948 Iams June 8, 1948 Mueller` Aug. 24, 1948 Southworth Feb. 1, 1949 Smith Mar. 15, 1949 Meier et al Mar. 15, 1949 FOREIGN PATENTS Country Date Australia Dec. 9, 1941 Great Britain Jan. 13, 1939 Germany Nov. 28, 1938 OTHER REFERENCES Practical Analysis of Ultra. High Frequencies, by Meagher and Markley, RCA Service Co. Inc.,

1 1 REFERENCES CITED Number f The following references are of record in the file of this patent. 2,411,872 UNITED STATES PATENTS 5 2,416,177 Number Name Date 2,430,568 1,336,951 Fulgne et al Apr. 13, 1920 2,436,421 1,808,867 Stone June 9, 1931 2,436,578 1,820,643 Arias Aug. 25, 1931 2,442,951 1,830,176 Schroter Nov. 3, 1931 10 2,447,768 1,860,123 Yagi May 24, 1932 2,460,401 2,049,070 Mathieu July 28, 1936 2,464,269 2,078,302 Woli Apr. 27, 1937 2,464,598 2,129,669 Bowen Sept. 13, 1938 2,129,712 Southworth Sept. 13, 1938 l5 2,161,842 Auison June 13, 1939 Number 2,206,683 Wolff July 2, 1940 114,368 2,206,923 Southworth July 9, 1940 498,805 2,255,042 Barrow sept. 9, 1941 668,231 2,273,447 Chl Feb. 17, 1942 20 2,283,568 Ohl May 19, 1942 2,283,935 King May 26, 1942 2,317,464 Katzin Apr. 27, 1943 1943 2,362,561 Katzin Nov. 14, 1944 

